The article presents the results of pilot injection wells treatments with a large volume of acid compositions, using a coiled tubing unit in JS2 formations of the Surgutneftrgas OJSC.
One of the problems in JS2 formations development is the difficulty of organizing a system of pressure maintenance, due to the low initial injectivity of new injectors and the fast falling injectivity of the active injection wells. The reasons for this are the low permeability and porosity of the JS2 formation, its complex geological structure, and drilling mud formation damage at the stage of well construction.
The basic method of well injectivity recovery is the treatment of the bottom-hole formation zone by the various acid compositions.
The acid treatments are aimed at restoring the filtration properties of the bottom-hole formation zone due to dissolution of the injected solids, carbonate and ferrous deposits, aggregates of interstitial clay. Average folds of increase in injectivity of the injectors in JS2 formation after acid treatments are 2.8-3 times, but the duration of the effect is small – 3-4 months on average. Fast falling injectivity is due to a range of reasons, among which the low penetrability of the acid compositions, secondary sedimentation, a small volume of injected acid and the absence of the flush stage of the bottom-hole formation zone in conventional treatments could be highlighted.
To increase the effect duration of acid treatments it was proposed to treat the bottom-hole formation zone with increased volumes of acid compositions compared to the conventional treatments, using a coiled tubing unit. Pilot tests of the given technology were conducted in 2013 – 2014, the results have shown that it allows to significantly increase the injectivity of the injectors compared to conventional treatments. This paper presents the criteria for well-candidates selection for large-volume treatments and moreover the prospects for further development of technology are noted.
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